Exoplanets in the Antarctic Sky. I. The First Data Release of AST3-II (CHESPA) and New Found Variables within the Southern CVZ of TESS
Résumé
Located at Dome A, the highest point of the Antarctic plateau, the Chinese
Kunlun station is considered to be one of the best ground-based photometric
sites because of its extremely cold, dry, and stable atmosphere(Saunders et al.
2009). A target can be monitored from there for over 40 days without diurnal
interruption during a polar winter. This makes Kunlun station a perfect site to
search for short-period transiting exoplanets. Since 2008, an observatory has
been built at Kunlun station and three telescopes are working there. Using
these telescopes, the AST3 project has been carried out over the last six years
with a search for transiting exoplanets as one of its key programs (CHESPA). In
the austral winters of 2016 and 2017, a set of target fields in the Southern
CVZ of TESS (Ricker et al. 2009) were monitored by the AST3-II telescope. In
this paper, we introduce the CHESPA and present the first data release
containing photometry of 26,578 bright stars (m_i < 15). The best photometric
precision at the optimum magnitude for the survey is around 2 mmag. To
demonstrate the data quality, we also present a catalog of 221 variables with a
brightness variation greater than 5 mmag from the 2016 data. Among these
variables, 179 are newly identified periodic variables not listed in the AAVSO
databasea), and 67 are listed in the Candidate Target List(Stassun et al.
2017). These variables will require careful attention to avoid false-positive
signals when searching for transiting exoplanets. Dozens of new transiting
exoplanet candidates will be also released in a subsequent paper(Zhang et al.
2018b).